Method And System For Hybrid Integration Of Optical Communication Systems

ABSTRACT

Methods and systems for hybrid integration of optical communication systems are disclosed and may include receiving a continuous wave (CW) optical signal in a silicon photonics die (SPD) from an optical source external to the SPD. The received CW optical signal may be processed based on electrical signals received from an electronics die bonded to the SPD via metal interconnects. A modulated optical signal may be received in the SPD from optical fibers coupled to the SPD. An electrical signal may be generated in the SPD based on the received modulated optical signal and communicated to the electronics die via the metal interconnects. The CW optical signal may be received from an optical source assembly coupled to the SPD and/or from one or more optical fibers coupled to the SPD. The received CW optical signal may be processed utilizing one or more optical modulators, which may comprise Mach-Zehnder interferometer modulators.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of U.S. application Ser. No.15/487,770 filed on Apr. 14, 2017, which is a continuation of U.S.application Ser. No. 15/144,611 filed on May 2, 2016, now U.S. Pat. No.9,625,665, which is a continuation of U.S. application Ser. No.13/568,406 filed on Aug. 7, 2012 now U.S. Pat. No. 9,331,096, which is acontinuation-in-part of U.S. application Ser. No. 12/554,449 filed onSep. 4, 2009, now U.S. Pat. No. 8,877,616. This application also makesreference to U.S. application Ser. No. 13/422,776, filed on Mar. 6,2012.

Each of the above cited references is hereby incorporated by referencein its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to semiconductor processing.More specifically, certain embodiments of the invention relate to amethod and system for hybrid integration of optical communicationsystems.

BACKGROUND OF THE INVENTION

As data networks scale to meet ever-increasing bandwidth requirements,the shortcomings of copper data channels are becoming apparent. Signalattenuation and crosstalk due to radiated electromagnetic energy are themain impediments encountered by designers of such systems. They can bemitigated to some extent with equalization, coding, and shielding, butthese techniques require considerable power, complexity, and cable bulkpenalties while offering only modest improvements in reach and verylimited scalability. Free of such channel limitations, opticalcommunication has been recognized as the successor to copper links.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present invention as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method for hybrid integration of optical communicationsystems, substantially as shown in and/or described in connection withat least one of the figures, as set forth more completely in the claims.

Various advantages, aspects and novel features of the present invention,as well as details of an illustrated embodiment thereof, will be morefully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of a photonic transceiver, in accordance withan embodiment of the invention.

FIG. 2A is a schematic illustrating an exemplary hybrid integrationphotonic transceiver, in accordance with an embodiment of the invention.

FIG. 2B is a perspective view of a hybrid integration photonictransceiver, in accordance with an embodiment of the invention.

FIG. 2C is a perspective view of a hybrid integration photonictransceiver, in accordance with an embodiment of the invention.

FIG. 3 is a schematic illustrating the hybrid integration of anelectronics die to a photonics die, in accordance with an embodiment ofthe invention.

FIG. 4A is a schematic illustrating a cross-section of exemplary metalinterconnect-coupled electrical and optoelectronic devices, inaccordance with an embodiment of the invention.

FIG. 4B is a schematic of an alternative face-to-face coupling ofelectronic and photonic chips, in accordance with an embodiment of theinvention.

FIG. 4C is a schematic of an alternative coupling of electronic andphotonic chips, in accordance with an embodiment of the invention.

FIG. 5 is a diagram illustrating exemplary metal pillars for couplingelectrical and photonics die, in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects of the invention may be found in a method and system forhybrid integration of optical communication systems. Exemplary aspectsof the invention may comprise receiving one or more continuous wave (CW)optical signals in a silicon photonics die from an optical sourceexternal to the photonics die. The one or more received CW opticalsignals may be processed based on electrical signals received from oneor more electronics die bonded to the silicon photonics die via metalinterconnects, which may comprise copper pillars, for example. Modulatedoptical signals may be received in the silicon photonics die from one ormore optical fibers coupled to the silicon photonics die. Electricalsignals may be generated in the silicon photonics die based on thereceived modulated optical signals and communicated to the one or moreelectronics die via the metal interconnects. The metal interconnects maycomprise copper pillars. The one or more CW optical signals may bereceived from an optical source assembly coupled to the siliconphotonics die and/or from one or more optical fibers coupled to thesilicon photonics die. The one or more received CW optical signals maybe processed utilizing one or more optical modulators, which maycomprise Mach-Zehnder interferometer modulators. The electrical signalsmay be generated in the silicon photonics die utilizing one or morephotodetectors integrated in the silicon photonics die. The opticalsignals may be communicated into and/or out of the silicon photonics dieutilizing grating couplers. The optical source may comprise one or moresemiconductor lasers. The hybrid integration optical communicationsystem may comprise a plurality of transceivers.

FIG. 1 is a block diagram of a photonic transceiver, in accordance withan embodiment of the invention. Referring to FIG. 1, there is shownoptoelectronic devices in a transceiver 100 comprising high speedoptical modulators 105A-105D, high-speed photodiodes 111A-111D, monitorphotodiodes 113A-113H, and optical devices comprising taps 103A-103K,optical terminations 115A-115D, and grating couplers 117A-117H. Thereare also shown electrical devices and circuits comprising transimpedanceand limiting amplifiers (TIA/LAs) 107A-107D, analog and digital controlcircuits 109, and control sections 112A-112D. Optical signals arecommunicated between optical and optoelectronic devices via opticalwaveguides fabricated in a photonics chip. Additionally, opticalwaveguides are indicated in FIG. 1 by the dashed ovals.

The high speed optical modulators 105A-105D comprise Mach-Zehnder orring modulators, for example, and enable the modulation of the CW laserinput signal. The high speed optical modulators 105A-105D are controlledby the control sections 112A-112D, and the outputs of the modulators areoptically coupled via waveguides to the grating couplers 117E-117H.Exemplary modulation techniques comprise amplitude shift keying (ASK),binary phase shift keying (BPSK), pulse amplitude modulation (PAM),quadrature amplitude modulation (QAM), quadrature phase shift keying(QPSK), and dual polarization quadrature phase shift keying (DP-QPSK).The taps 103D-103K comprise four-port optical couplers, for example, andare utilized to sample the optical signals generated by the high speedoptical modulators 105A-105D, with the sampled signals being measured bythe monitor photodiodes 113A-113H. The unused branches of the taps103D-103K are terminated by optical terminations 115A-115D to avoid backreflections of unwanted signals.

The grating couplers 117A-117H comprise optical gratings that enablecoupling of light into and out of the chip. The grating couplers117A-117D are utilized to couple light received from optical fibers intothe chip, and may comprise polarization independent grating couplers.The grating couplers 117E-117H are utilized to couple light from thechip into optical fibers. The optical fibers may be epoxied, forexample, to the chip, and may be aligned at an angle from normal to thesurface of the chip to optimize coupling efficiency.

The high-speed photodiodes 111A-111D convert optical signals receivedfrom the grating couplers 117A-117D into electrical signals that arecommunicated to the TIA/LAs 107A-107D for processing. The analog anddigital control circuits 109 may control gain levels or other parametersin the operation of the TIA/LAs 107A-107D. The TIA/LAs 107A-107D, theanalog and digital control circuits 109, and the control sections112A-112D may be integrated on an electronics chip that may be bonded tothe silicon photonics chip via metal interconnects. In an exemplaryscenario, the metal interconnects may comprise copper pillars. In thismanner, electronic and photonic performance may be optimizedindependently on different fabrication technology platforms. In anexemplary scenario, the electronics die may comprise CMOS die, but theinvention is not so limited. Accordingly, any semiconductor technologymay be utilized to fabricate the electronic die, such as CMOS, Bi-COMS,SiGe, or III-V processes. The TIA/LAs 107A-107D may then communicateelectrical signals to other circuitry on the electronics chip.

The TIA/LAs 107A-107D may comprise narrowband, non-linear optoelectronicreceiver circuitry. Accordingly, the narrowband receiver front-end maybe followed by a restorer circuit, such as, for example, a non-return tozero (NRZ) level restorer circuit. A restorer circuit limits thebandwidth of the optical receiver in order to decrease the integratednoise, thereby increasing the signal to noise ratio. An NRZ levelrestorer may be used to convert the resulting data pulses back into NRZdata.

The control sections 112A-112D comprise electronic circuitry that enablemodulation of the CW laser signal received from the taps 103A-103C. Thehigh speed optical modulators 105A-105D require high-speed electricalsignals to modulate the refractive index in respective branches of aMach-Zehnder interferometer (MZI), for example.

In an embodiment of the invention, the integration of all optical andoptoelectronic devices required for a transceiver into a single siliconphotonics chip, and of all required electronic devices on one or moreelectronics chips, enables optimized performance of the resulting singlehybrid package. In this manner, electronic device performance may beoptimized independently of the optimization of photonic devices in thesilicon photonic chip. For example, the electronics chip may beoptimized on a 32 nm CMOS process, while the photonics chip may beoptimized on a 130 nm CMOS node. Additionally, the electronics orphotonics chips may be fabricated utilizing technologies other thanCMOS, such as SiGe or bipolar-CMOS (Bi-CMOS). The electronics devicesmay be placed on the electronics chip such that they are locateddirectly above their associated photonics devices when bonded to thephotonics chip. For example, the control sections 112A-112D may belocated on the electronics chip such that they lie directly above thehigh-speed optical modulators 105A-105D and can be coupled by lowparasitic copper pillars.

In an exemplary embodiment, the hybrid transceiver 100 comprises fouroptoelectronic transceivers with one optical source, and enablescommunication of optical signals vertically to and from the surface ofthe photonics chip, thereby enabling in an exemplary embodiment, the useof CMOS processes and structures, including a CMOS guard ring. Thephotonics chip may comprise both active devices, such as photodetectorsand modulators, and passive devices, such as waveguides, splitters,combiners, and grating couplers, thereby enabling photonic circuits tobe integrated on silicon chips.

FIG. 2A is a schematic illustrating an exemplary hybrid integrationphotonic transceiver, in accordance with an embodiment of the invention.Referring to FIG. 2A, there is shown a hybrid integration photonictransceiver 200 comprising a printed circuit board (PCB)/substrate 201,a photonic CMOS die 203, an electronic CMOS die 205, metal interconnects207, an optical source module 209, an optical input/output (I/O) 211,wire bonds 213, optical epoxy 215, and optical fibers 217.

The PCB/substrate 201 may comprise a support structure for thetransceiver 200, and may comprise both insulating and conductivematerial for isolating devices as well as providing electrical contactfor active devices on the photonics die 203 as well as to devices on theelectronics die 205 via the photonics die 203. In addition, thePCB/substrate may provide a thermally conductive path to carry away heatgenerated by devices and circuits in the electronics die 205 and theoptical source module 209.

The photonics die 203 may comprise a silicon chip with active andpassive optical devices such as waveguides, modulators, photodetectors,grating couplers, taps, and combiners, for example. The photonics die203 may also comprise metal interconnects 207 for coupling theelectronics die 205 to the photonics die 203, as well as gratingcouplers for coupling light into the die from the optical source module209 and into/out of the die via the optical I/O 211. In addition, thephotonics die 203 may comprise through-substrate-vias (TSVs), not shown,for electrical interconnection through the die, such as between thePCB/substrate 201 and the electronics die 205. Optical interfaces mayalso be facilitated by the optical epoxy 215, providing both opticaltransparency and mechanical fixation.

The electronics die 205 may comprise a chip that provides all therequired electronic functions of the photonic transceiver 200. Theelectronics die 205 may comprise a single chip or a plurality of diecoupled to the photonics chip 203 via the metal interconnects 207. Theelectronics die 205 may comprise TIA's, LNAs, and control circuits forprocessing optical signals in the photonics chip 203. For example, theelectronics die 205 may comprise driver circuitry for controllingoptical modulators in the photonics die 203 and variable gain amplifiersfor amplifying electrical signals received from photodetectors in thephotonics die 203. By incorporating photonics devices in the photonicsdie 203 and electronic devices in the electronics die 205, the processesfor each chip may be optimized for the type of devices incorporated.

The metal interconnects 207 may comprise linear or 2D arrays of metalpillars, for example, to provide electrical contact between thephotonics die 203 and the electronics die 205. In an exemplary scenario,the metal interconnects 207 may comprise copper pillars, or any othersuitable metal for semiconductor contacts, such as stud bumps or solderbumps. Accordingly, the metal interconnects 207 may provide electricalcontact between photodetectors in the photonics die 203 and associatedreceiver circuitry in the electronics die 205. In addition, the metalinterconnects 207 may provide mechanical coupling of the electronics andphotonics die, and may be encapsulated with underfill to protect themetal and other surfaces.

The optical source module 209 may comprise an assembly with an opticalsource, such as a semiconductor laser, and associated optical elementsto direct one or more optical signals into the photonics die 203. Anexample of the optical source module is described in U.S. patentapplication Ser. No. 12/500,465 filed on Jul. 9, 2009, which is herebyincorporated in its entirety. In another exemplary scenario, the opticalsignal or signals from the optical source assembly 209 may be coupledinto the photonics die 203 via optical fibers affixed above gratingcouplers in the photonics die 203.

The optical I/O 211 may comprise an assembly for coupling the opticalfibers 217 to the photonics die 203. Accordingly, the optical I/O 211may comprise mechanical support for one or more optical fibers and anoptical surface to be coupled to the photonics die 203, such as by theoptical epoxy 215.

In operation, continuous-wave (CW) optical signals may be communicatedinto the photonics die 203 from the optical source module 209 via one ormore grating couplers in the photonics die 203. Photonic devices in thephotonics die 203 may then process the received optical signal. Forexample, one or more optical modulators may modulate the CW signal basedon electrical signals received from the electronics die 205. Electricalsignals may be received from the electronics die 205 via the metalinterconnects 207. By integrating modulators in the photonics die 203directly beneath the source of the electrical signals in the electronicsdie 205, signal path lengths may be minimized, resulting in very highspeed performance. For example, utilizing metal pillars with <20 fFcapacitance, speeds of 50 GHz and higher can be achieved.

The modulated optical signals may then be communicated out of thephotonics die 203 via grating couplers situated beneath the optical I/O211. In this manner, high-speed electrical signals generated in theelectronics die 205 may be utilized to modulate a CW optical signal andsubsequently communicated out of the photonics die 203 via the opticalfibers 217.

Similarly, modulated optical signals may be received in the photonicsdie 203 via the optical fibers 217 and the optical I/O 211. The receivedoptical signals may be communicated within the photonics die 203 viaoptical waveguides to one or more photodetectors integrated in thephotonics die 203. The photodetectors may be integrated in the photonicsdie 203 such that they lie directly beneath the associated receiverelectronics circuitry in the electronics die 205 when bonded andelectrically coupled by the low parasitic capacitance metalinterconnects 207.

The hybrid integration of electronics die on photonic die via metalinterconnects enables very high speed optical transceivers utilizingstandard semiconductor processes, such as CMOS, Bi-CMOS, or Si—Ge. Inaddition, integrating separate photonic and electronic die enables theindependent optimization of the performance of electronic and photonicfunctions within the respective semiconductor processes.

FIG. 2B is a perspective view of a hybrid integration photonictransceiver, in accordance with an embodiment of the invention.Referring to FIG. 2B, there is shown the PCB/substrate 201, thephotonics die 203, electronics die 205, the metal interconnects 207, theoptical source assembly 209, and wire bonds 213.

The electronics die 205 are shown prior to bonding to the surface of thephotonics die 203 via the metal interconnects 207, as illustrated by thedashed arrows below each die. While two electronics die 205 are shown inFIG. 2B, it should be noted that the invention is not so limited.Accordingly, any number of electronics die may be coupled to thephotonics die 203 depending on number of transceivers, the particularsemiconductor process node utilized, thermal conductance, and spacelimitations, for example.

In an exemplary embodiment, electronic functions may be integrated intothe electronics die 205 and photonics circuitry may be integrated intothe photonics die 203 utilizing independent semiconductor processes. Theelectronics die 205 may comprise electronic devices associated withphotonic devices in the photonics die 203, thereby minimizing electricalpath lengths while still allowing independent performance optimizationof electronic and photonic devices. For example, a CMOS process thatresults in the highest electronics performance, such as the fastestswitching speed, may not be optimum for photonics performance.Similarly, different technologies may be incorporated in the differentdie. For example, SiGe processes may be used for photonic devices suchas photodetectors, and 32 nm CMOS process, or even a SiGe or Bi-CMOSprocess, may be used for electronic devices on the electronics die 205.

The photonics die 203 may comprise photonic circuits, whereby opticalsignals may be received, processed, and transmitted out of the photonicsdie 203. The optical source assembly 209 may provide a CW optical signalto the photonics die 203, with the photonics circuitry in the photonicsdie 203 processing the CW signal. For example, the CW signal may becoupled into the photonics die 203 via grating couplers, communicated tovarious locations on the die via optical waveguides, modulated byMach-Zehnder interferometer (MZI) modulators, and communicated out ofthe photonics die 203 into optical fibers. In this manner, the hybridintegration of a plurality of high performance optical transceivers isenabled in semiconductor processes.

FIG. 2C is a perspective view of a hybrid integration photonictransceiver, in accordance with an embodiment of the invention.Referring to FIG. 2C, there is shown the PCB/substrate 201, thephotonics die 203, electronics die 205, the optical source assembly 209,the optical I/O 211, wire bonds 213, and optical fibers 217.

The electronics die 205 are shown bonded to the surface of the photonicsdie 203 via metal pillars. While two electronics die 205 are shown inFIG. 2C, it should again be noted that the invention is not so limited.Accordingly, any number of electronics die may be coupled to thephotonics die 203 depending on number of transceivers, the particularCMOS node utilized, and space limitations, for example.

In an exemplary embodiment, electronic functions may be integrated intothe electronics die 205 and photonics circuitry may be integrated intothe photonics die 203 utilizing independent semiconductor processes. Theelectronics die 205 may comprise electronic devices associated withphotonic devices in the photonics die 203, thereby minimizing electricalpath lengths while still allowing independent performance optimizationof electronic and photonic devices. Different technologies may beincorporated in the different die. For example, a Ge selective epitaxyprocess may be used for photodetectors in the photonics die 203, and a32 nm CMOS process may be used for electronic devices on the electronicsdie 205.

The photonics die 203 may comprise photonic circuits, whereby opticalsignals may be received, processed, and transmitted out of the photonicsdie 203. The optical source assembly 209 may provide a CW optical signalto the photonics die 203 and biased by voltages coupled to the opticalsource assembly 209 via wire bonds 213. Photonics circuitry in thephotonics die 203 may then process the CW signal. For example, the CWsignal may be coupled into the photonics die 203 via grating couplers,communicated to various locations on the die via optical waveguides,modulated by MZI modulators, and communicated out of the photonics die203 into the optical fibers 217 via the optical I/O 211. Heat may beconducted away from the die via the PCB/substrate 201. In this manner,the hybrid integration of a plurality of high performance opticaltransceivers is enabled in standard semiconductor processes.

FIG. 3 is a schematic illustrating the hybrid integration of anelectronics die to a photonics die, in accordance with an embodiment ofthe invention. Referring to FIG. 3, there is shown an electronics die205, metal interconnects 207, and a photonics die/interposer 300. Thephotonics die/interposer 300 may comprise grating couplers 301, apolarization splitting grating coupler 303, a photodetector 305, anoptical modulator 307, TSVs 309, and optical waveguides 311.

The metal interconnects 207 provide both electrical and mechanicalcoupling between the electronics die 205 and the photonicsdie/interposer 300. The grating couplers 301 provide for the coupling oflight into and/or out of the photonics die/interposer 300. Similarly,the polarization-splitting grating coupler 303 may enable the couplingof two polarizations of light into and/or out of the photonicsdie/interposer 300.

The modulator 307 may comprise a MZI modulator, for example, and may beoperable to modulate an optical signal based on electrical signalsreceived from the electronics die 205 via the metal interconnects 207.In an exemplary scenario, a CW optical signal may be received from anoptical source via one of the grating couplers 301, communicated via theoptical waveguides 311, modulated by the optical modulator 307,communicated back by the optical waveguides 311, and out of thephotonics die/interposer 300 via the other grating coupler 301.

The photodetector 305 may comprise a semiconductor photodiode, forexample, and may be operable to convert a received optical signal to anelectrical signal. In an exemplary scenario, optical signals withperpendicular polarizations may be received by thepolarization-splitting grating coupler 303, communicated via thewaveguides 311, converted to an electrical signal by the photodetector305, with the resulting electrical signals communicated to theelectronics die 205 via the metal interconnects 207. The electricalsignals may be further processed by electronics in the electronics die205 and/or communicated to other circuitry via wire bonds or the metalinterconnects 207 and the TSVs 309.

The photonics die/interposer 300 comprises a silicon photonics die thatmay provide photonic circuits for a plurality of electronics die,thereby reducing or eliminating electrical interconnects betweenhigh-speed electronics. This may be utilized for high-speed memoryaccess, high-speed processor interconnects, and coupling a plurality ofhigh-speed electronics chips, for example.

FIG. 4A is a schematic illustrating a cross-section of exemplary metalinterconnect-coupled electrical and optoelectronic devices, inaccordance with an embodiment of the invention. Referring to FIG. 4A,there is shown a hybrid integrated semiconductor structure 400comprising a silicon photonics substrate/chip/die 450, an electronicssubstrate/chip/die 460, and a metal layer 427 for substrate/chipphysical and electrical coupling. The silicon photonicssubstrate/chip/die 450 comprises optical devices 420 and associatedlayers, and the electronics substrate/chip/die 460 comprises transistors410A and 410B and associated layers. The layers of the die are utilizedto fabricate the transistors 410A and 410B and the optical devices 420,to isolate, and to provide electrical connection to the devices, forexample.

The silicon photonics substrate/chip/die 450 comprises a substrate 401A,a buried oxide 403, a Si-layer 405, a contact layer 415A, a metal 1layer 417A, and through-silicon vias (TSVs) 443A and 443B. The opticaldevices 420 comprise doped and/or undoped regions of the Si-layer 405, asalicide block 413, doped contact regions 435 and 437, etched region439, and the Ge-layer 445. The salicide block 413 comprises a layer ofmaterial to prevent the silicon of the optical devices 420 and otheroptical devices from being salicided during a standard CMOS process. Ifsilicon in the optical devices was salicided, large optical losses wouldresult. Additionally, the salicide block 413 blocks unwanted implantsinto the waveguides and other optical devices, which would also causeunwanted loss. The salicide block 413 may be etched to the Si-layer 405so that the Ge-layer 445 may be deposited. The Ge-layer 445 may beutilized in a photodetector device, for example. In addition, etchedregions 439 in the Si-layer 405 may be utilized for optical confinement.The etch regions 439 may be refilled with a low-k dielectric, forexample, or may comprise an air gap with no refill material. Fillmaterial may comprise silicon oxide or oxynitride materials, forexample.

The silicon electronics substrate/chip/die 460 comprises a siliconsubstrate 401B, a well 407, a contact layer 415B, a metal 1 layer 417B,a last metal layer 423, a passivation layer 425, and the metal layer427. The metal 1 layer 417B, the last metal layer 423, and the metallayer 427 provide electrical contact between layers and to electricaland optoelectronics devices, such as the transistors 410A and 410B andthe optical devices 420. The contact layer 415 also enables electricalcontact to the devices while providing electrical isolation betweendevices by incorporating insulating materials between conductive vias.

The transistor 410A and 410B comprise bulk transistors with source anddrain regions formed in the well 407 or the substrate 401B,respectively, from dopant implant processes, for example, as well as agate 431, and a passivation layer 433. The gate 431 may comprise metalor polysilicon, for example, and may be isolated from the well 407 by athin oxide layer (not shown).

In an embodiment of the invention, separate semiconductor processes maybe utilized to fabricate the silicon photonics substrate/chip/die 450and the electronics substrate/chip/die 460 so that the processes may beoptimized for each type of device. In an exemplary scenario, theseparate semiconductor processes may comprise different CMOS nodes, ormay comprise different technologies entirely, such as CMOS and SiGe.

The wafers, or alternatively diced chips, may then be bonded together toform an optoelectronic hybrid module utilizing metal layers such asmetal pillars. In this manner, layer thicknesses and doping levels maybe configured for the best electronic and photonic performance in therespective structure without the tradeoffs in performance associatedwith fabricating electronic and photonic structures concurrently.

FIG. 4B is a schematic of an alternative face-to-face coupling ofelectronic and photonic chips, in accordance with an embodiment of theinvention. Referring to FIG. 4B, there is shown the silicon photonicschip 450 and the electronics chip 460 coupled utilizing an interconnectlayer 427, which may comprise metal pillars, stud bumps, or solderbumps, for example.

The silicon photonics chip 450 may comprise a substrate 401C, opticaldevices 420, and metal layers 430. The electronics chip 460 may comprisea substrate 401D, transistors 410C and 410D, and the metal layers 430.Each of these elements may be similar to the like-named elements of FIG.4A.

The embodiment shown in FIG. 4B may be similar to that shown in FIG. 4A,but with the electronics and photonics chips bonded face-to-face,thereby removing the need for through-substrate-vias (TSVs).

FIG. 4C is a schematic of an alternative coupling of electronic andphotonic chips, in accordance with an embodiment of the invention.Referring to FIG. 4C, there is shown the silicon photonics chip 450 andthe electronics chip 460 coupled utilizing interconnects 427, which maycomprise metal pillars, stud bumps, or solder bumps, for example.

The silicon photonics chip 450 may comprise a substrate 401E, opticaldevices 420, and metal layers 430. The electronics chip 460 may comprisea substrate 401F, transistors 410C and 410D, and the metal layers 430.Each of these elements may be similar to the like-named elements ofFIGS. 4A and 4B.

The embodiment shown in FIG. 4C may be similar to that shown in FIG. 4A,but with the silicon photonics chip 450 on bottom and the electronicschip 460 on top. In this scenario, the electrical contacts may be madeutilizing TSVs and metal interconnects, such as metal pillars or bumps.

FIG. 5 is a diagram illustrating exemplary metal interconnects forcoupling electrical and photonics die, in accordance with an embodimentof the invention. Referring to FIG. 5, there is shown cross-section andperspective views of the metal interconnects 207. The exemplary copperpillars shown comprise widths on the order of 50 microns, but smallerdiameters may be utilized for reduced parasitic capacitance. Inaddition, a tin/silver cap layer may be utilized for mechanical bondingand electrical contact, i.e. soldering. The dimensions of the metalinterconnects may be adjusted based on speed requirements, devicedensity, thermal properties, and capacitance and electrical resistancerequirements, for example.

In an embodiment of the invention, a method and system are disclosed forhybrid integration of optical communication systems. In this regard,receiving one or more continuous wave (CW) optical signals in a siliconphotonics die 203/300 from an optical source 209 external to the siliconphotonics die 203/300. The one or more received CW optical signals maybe processed based on electrical signals received from one or moreelectronics die 205 bonded to the silicon photonics die 203/300 viametal interconnects 207.

Modulated optical signals may be received in the photonics die 203/300from one or more optical fibers 217 coupled to the silicon photonics die203/300. Electrical signals may be generated in the silicon photonicsdie 203/300 based on the received modulated optical signals andcommunicated to the one or more electronics die 205 via the metalinterconnects 207. The metal interconnects 207 may comprise copperpillars, for example. The one or more CW optical signals may be receivedfrom an optical source assembly 209 coupled to the silicon photonics die203/300 and/or from one or more optical fibers 217 coupled to thesilicon photonics die 203/300.

The one or more received CW optical signals may be processed utilizingone or more optical modulators 105A-105D/307, which may compriseMach-Zehnder interferometer modulators, for example. The electricalsignals may be generated in the silicon photonics die 203/300 utilizingone or more photodetectors 111A-111D/305 integrated in the siliconphotonics die 203/300. The optical signals may be communicated intoand/or out of the silicon photonics die 203/300 utilizing gratingcouplers 117A-117H/301/303. The optical source 209 may comprise one ormore semiconductor lasers 101. The hybrid integration opticalcommunication system 100 may comprise a plurality of transceivers105/112/117/107/111 (A-F).

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiments disclosed, but that the present inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for communication, the methodcomprising: in an optical communication system comprising a siliconphotonics die and one or more electronics die bonded to said siliconphotonics die utilizing metal interconnects: receiving a continuous wave(CW) non-modulated optical signal in said silicon photonics die from anoptical source external to said silicon photonics die; modulating saidreceived CW non-modulated optical signal in said silicon photonics dieusing a first electrical signal received from said one or moreelectronics die via one or more of said metal interconnects; receiving amodulated optical signal in said silicon photonics die; generating asecond electrical signal in said silicon photonics die based on saidreceived modulated optical signal; and communicating said secondelectrical signal to at least one of said one or more electronics dievia one or more of said metal interconnects.
 2. The method according toclaim 1, wherein said metal interconnects comprise copper pillars. 3.The method according to claim 1, comprising receiving said CWnon-modulated optical signal from an optical source assembly coupled tosaid silicon photonics die.
 4. The method according to claim 1,comprising receiving said CW non-modulated optical signal from anoptical fiber coupled to said silicon photonics die.
 5. The methodaccording to claim 1, comprising modulating said received CWnon-modulated optical signal utilizing one or more optical modulatorsintegrated in said silicon photonics die.
 6. The method according toclaim 5, wherein said one or more optical modulators compriseMach-Zehnder interferometer modulators.
 7. The method according to claim1, comprising generating said second electrical signal utilizing one ormore photodetectors integrated in said silicon photonics die.
 8. Themethod according to claim 1, comprising communicating optical signalsinto and/or out of said silicon photonics die utilizing gratingcouplers.
 9. The method according to claim 1, wherein said opticalsource comprises one or more semiconductor lasers.
 10. The methodaccording to claim 1, wherein said optical communication systemcomprises a plurality of transceivers.
 11. A system for communication,the system comprising: an optical communication system comprising asilicon photonics die and one or more electronics die bonded to saidsilicon photonics die utilizing metal interconnects, said opticalcommunication system being operable to: receive a continuous wave (CW)non-modulated optical signal in said silicon photonics die from anoptical source external to said silicon photonics die; modulate saidreceived CW non-modulated optical signal in said silicon photonics dieusing a first electrical signal received from said one or moreelectronics die via one or more of said metal interconnects; receive amodulated optical signal in said silicon photonics die; generate asecond electrical signal in said silicon photonics die based on saidreceived modulated optical signal; and communicate said secondelectrical signal to at least one of said one or more electronics dievia one or more of said metal interconnects.
 12. The system according toclaim 11, wherein said metal interconnects comprise copper pillars. 13.The system according to claim 11, wherein said optical communicationsystem is operable to receive said CW non-modulated optical signal froman optical source assembly coupled to said silicon photonics die. 14.The system according to claim 11, wherein said optical communicationsystem is operable to receive said CW non-modulated optical signal froman optical fiber coupled to said silicon photonics die.
 15. The systemaccording to claim 11, wherein said optical communication system isoperable to modulate said received CW non-modulated optical signalutilizing one or more optical modulators integrated in said siliconphotonics die.
 16. The system according to claim 15, wherein said one ormore optical modulators comprise Mach-Zehnder interferometer modulators.17. The system according to claim 11, wherein said optical communicationsystem is operable to generate said second electrical signal utilizingone or more photodetectors integrated in said silicon photonics die. 18.The system according to claim 11, wherein said optical communicationsystem is operable to communicate optical signals into and/or out ofsaid silicon photonics die utilizing grating couplers.
 19. The systemaccording to claim 11, wherein said optical source comprises one or moresemiconductor lasers.
 20. A system for communication, the systemcomprising: an optical communication system comprising a siliconphotonics die and one or more electronics die bonded to said siliconphotonics die utilizing metal pillars, said optical communication systembeing operable to: receive a continuous wave (CW) non-modulated opticalsignal in said silicon photonics die from an optical source external tosaid silicon photonics die; modulate said received CW non-modulatedoptical signal based on a first electrical signal received from said oneor more electronics die via one or more of said metal pillars; receive amodulated optical signal in said silicon photonics die; generate asecond electrical signal utilizing a photodetector in said siliconphotonics die based on said received modulated optical signal; andcommunicate said second electrical signal to said one or moreelectronics die via one or more of said metal pillars.